1. Field of the Invention
The present invention relates to a server that distributes meteorological information to a vehicle and/or a vehicle-mounted navigation apparatus, a vehicle and a vehicle-mounted navigation apparatus that request meteorological information to the server, and a meteorological information distribution system.
2. Related Art
There is a method for distributing meteorological information to navigation apparatuses in which a content provider receives meteorological information obtained from meteorological satellites, the Automated Meteorological Data Acquisition System (AMeDAS), or the like, from organizations, such as the Japan Weather Association, and distributes it to navigation apparatuses as it is. In addition, the invention disclosed in Japanese Unexamined Patent publication No. 2003-66160 is a technique in which emergency information relating to an area is distributed in response to a request from a terminal, i.e., navigation apparatus.
However, when the meteorological data obtained from the meteorological satellites, the AMeDAS, or the like, is distributed to the whole nation as it is, the volume of the data tends to increase because wide-area meteorological data is distributed. As a result, when the data is received by a vehicle or a vehicle-mounted navigation apparatus, a lot of communication time and high communication charges are required for receiving it, making the method inappropriate. Furthermore, weather advisories, warnings, or the like, that are distributed are issued based on criteria which are different from area to area. In general, updates of such weather advisories, warning, or the like based on different area-to-area criteria is infrequent. As a result, weather warnings or the like which are appropriate for that area may not be always issued.
Furthermore, in the method disclosed in the above-described Japanese Unexamined Patent publication No. 2003-66160, although it is possible to display information relating to areas centered on a position selected by a user, the communication link has to be maintained to achieve this. Furthermore, the contents of the information are fixed and cannot be changed from season to season or from area to area. In addition, since a large volume of data, such as AMeDAS data, is also sent from the server, the large size of the data has to be transmitted, which may result in waste of communication time and communication charges when wireless communication is used, as in the case of a vehicle or a vehicle-mounted navigation apparatus.
In principle, meteorological information that is required, or types of weather warning that are frequently issued, generally vary from area to area or from season to season. For example, in the metropolitan area including Tokyo, the public transportation systems are often severely disrupted by even a small amount of snowfall, so that frequently-updated information is generally desired. For this reason, in the Tokyo metropolitan area, it is required that information specific to certain areas or seasons be distributed, such as distributing frequently-updated meteorological data from the AMeDAS with a higher priority.
In addition, the data size may be increased by simply distributing information desired for that area. For example, since the size of the meteorological data from the AMeDAS is usually large, the size of the entire data to be sent is increased when the data from the AMeDAS is distributed with a higher priority, which may cause waste of communication time and communication charges.